P0301
Fix within a few daysYour engine's computer detected that cylinder 1 is not firing correctly.
Code P0301 means cylinder 1 is misfiring. Common causes: Spark plug (40%), ignition coil (30%), fuel injector (15%). Drivability: Yes, for short trips only. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0301?
Yes, for short trips only
Essential trips under 10 miles, avoid highways and heavy acceleration. Fix within a few days.
Stop driving immediately if: Flashing Check Engine Light, loud knocking noises, burning smell, rotten egg smell from exhaust, significant power loss or engine shaking.
Symptoms of P0301
- 1Engine runs rough or shakes, especially at idle
- 2Loss of engine power
- 3Reduced fuel economy
- 4Engine hesitation or stumbling during acceleration
- 5Check Engine Light is on, and may flash during severe misfires
Common Causes of P0301
Parts most likely causing this code, ranked by probability
A worn, fouled, or damaged spark plug in cylinder 1 prevents proper ignition of the fuel-air mixture.
40% of P0301 cases are fixed by replacing the spark plug
A failing ignition coil for cylinder 1 cannot generate enough voltage to create a strong spark, leading to a misfire.
30% of P0301 cases are fixed by replacing the ignition coil
A clogged, dirty, or faulty fuel injector for cylinder 1 fails to deliver the correct amount of fuel, causing a lean or rich misfire.
15% of P0301 cases are fixed by replacing the fuel injector
An air leak near cylinder 1's intake runner or a general vacuum leak can lean out the air-fuel mixture, causing a misfire.
5% of P0301 cases are fixed by repairing a vacuum leak
Low compression in cylinder 1, due to issues like worn piston rings, burnt valves, or a blown head gasket, prevents proper combustion.
5% of P0301 cases are fixed by addressing an engine compression issue
A rare but possible cause, a faulty ECM/PCM can incorrectly command ignition or fuel delivery to cylinder 1, causing a misfire.
5% of P0301 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the spark plug and ignition coil for cylinder 1 for any obvious damage, cracks, or corrosion.
- Listen for any hissing sounds around the intake manifold that could indicate a vacuum leak.
How to Diagnose P0301
- 1Check for a flashing Check Engine Light, which indicates a severe misfire.
- 2Inspect the spark plug and ignition coil for cylinder 1. Look for signs of damage, oil fouling, or corrosion.
- 3Swap the ignition coil from cylinder 1 with a coil from a different cylinder (e.g., cylinder 2). If the misfire moves to the new cylinder (e.g., P0302), the coil is faulty.
- 4Swap the spark plug from cylinder 1 with a plug from a different cylinder. If the misfire moves, the spark plug is faulty.
- 5Perform a fuel pressure test and check the fuel injector pulse for cylinder 1 using a noid light or oscilloscope.
- 6Perform a compression test on cylinder 1 to check for internal engine issues.
- 7Check for vacuum leaks around the intake manifold and vacuum lines.
P0301 on Popular Vehicles
Toyota Camry
2007-2024P0301 on Toyota Camry models is frequently linked to a failing ignition coil or a worn spark plug. Fuel injectors are less common but still a possibility. Always check for oil in the spark plug tubes from a leaking valve cover gasket.
70% fixed by ignition coil or spark plug replacement
Honda Accord
2003-2024Honda Accord P0301 codes are often resolved by replacing the ignition coil or spark plug for cylinder 1. On some older models, a failing EGR valve can cause misfires, though it usually triggers other codes as well.
75% fixed by ignition coil or spark plug replacement
Ford F-150
2004-2024For Ford F-150 trucks, especially those with V8 engines, P0301 is a very common code for a failing ignition coil or spark plug. On 3-valve Triton engines (2004-2008), spark plug removal can be problematic, requiring special tools.
80% fixed by ignition coil or spark plug replacement
Frequently Asked Questions
What does P0301 mean?
P0301 indicates that your engine's computer has detected a misfire specifically in cylinder number 1. This means cylinder 1 is not contributing power to the engine as it should.
Can I drive with P0301?
Yes, you can drive for short, essential trips only. If the Check Engine Light is flashing, stop driving immediately. Continued driving with a misfire can cause serious damage to your catalytic converter, turning a simple repair into a very expensive one.
Will P0301 clear itself?
No, P0301 will not clear itself. The underlying issue causing the misfire must be diagnosed and repaired. Once the repair is complete, you can clear the code with an OBD-II scanner, or it will clear after several drive cycles if the problem is resolved.
How do I fix P0301 myself?
Start by inspecting and replacing the spark plug for cylinder 1. If that doesn't work, swap the ignition coil for cylinder 1 with another cylinder's coil to see if the misfire moves. If it does, replace the coil. If not, you may need to check the fuel injector or perform a compression test.
How much does it cost to fix P0301?
DIY repair costs range from $15 for a single spark plug to $100-$200 for an ignition coil or fuel injector. Professional repair costs typically range from $150 to $500, depending on the part and labor involved.
P0301 keeps coming back - why?
P0301 keeps coming back because the root cause has not been fully addressed. This often happens if you only replaced one component (like a spark plug) when the issue was actually the ignition coil, fuel injector, or a deeper engine problem like low compression or a vacuum leak.
Will P0301 fail emissions/smog test?
Yes, P0301 will cause your vehicle to fail an emissions or smog test. A misfire indicates incomplete combustion, leading to higher emissions and the Check Engine Light being on, which is an automatic failure.
What's the difference between P0301 and P0300?
P0301 specifically indicates a misfire in cylinder 1. P0300 indicates a 'Random/Multiple Cylinder Misfire Detected,' meaning the misfire is not isolated to a single cylinder or is jumping between cylinders. P0301 points you directly to cylinder 1, while P0300 requires more general diagnosis.
P0301 on Ford F-150 - what's common?
On many Ford F-150 models, especially those with Triton engines, P0301 is very commonly caused by a failing ignition coil or a worn spark plug. The spark plugs can be difficult to remove on some older Triton engines, sometimes breaking off in the head.
Questions to Ask Your Mechanic
Did you perform a compression test on cylinder 1?
Good answer: Yes, compression on cylinder 1 is [X] PSI, which is within specification. This rules out major internal engine damage.
Did you check for vacuum leaks around the intake manifold?
Good answer: Yes, I sprayed carb cleaner around the intake manifold and vacuum lines, and the engine RPM did not change, indicating no external vacuum leaks.
Repair Cost Estimate
DIY Repair
Parts only
$15-$200
Shop Repair
Parts + labor
$150-$500
Save $135-$300 by doing it yourself
Difficulty
intermediate
Time
0.5-2 hours
Intermediate - requires basic mechanical skills and an OBD-II scanner. Swapping coils and plugs is manageable, but diagnosing fuel injectors or compression issues requires more specialized tools and knowledge.
Cost of Waiting
Continued misfires send unburned fuel into your exhaust system, which can rapidly overheat and destroy your catalytic converter. A $15-$100 spark plug or coil job now prevents a $800-$2,500 converter replacement later.
While You're In There...
If your vehicle uses spark plug wires, they wear out over time and can cause misfires. Replacing them with the spark plugs ensures a complete ignition system refresh.
These rubber boots and springs connect the coil to the spark plug and can degrade, causing poor electrical contact. They are inexpensive and easy to replace when the coil is off.
Applying dielectric grease to the spark plug boot helps seal out moisture and prevents corrosion, ensuring good electrical connection and easier future removal.
Tools You'll Need
- OBD-II Scanner
- Spark plug socket set
- Ratchet and extensions
- Torque wrench
- Ignition coil puller (optional, but helpful)
- Multimeter (for testing coils/injectors)
- Compression tester (if misfire persists)
P0301 is a very common engine code. Most repairs are straightforward, involving a spark plug or ignition coil, and your engine will run smoothly again afterward.
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Your Next Steps
Step 1: Inspect the spark plug and ignition coil for cylinder 1. Look for oil, cracks, or excessive wear.
Step 2: If no obvious issues, swap the ignition coil from cylinder 1 with another cylinder. If the misfire moves, replace the coil. If not, swap the spark plug. If the misfire moves, replace the spark plug.
Step 3: If swapping parts doesn't fix it, perform a compression test on cylinder 1. If compression is low, you have a more serious internal engine issue. Otherwise, consider testing the fuel injector or checking for vacuum leaks.